This invention relates generally to hydraulic door closers and more particularly to valves for regulating speed of opening and closing of a door having such a closer.
Door closers typically consist of a housing with a fluid filled cylindrical bore in which a spring biases a rack-bearing piston in one direction. A pinion is meshed with the rack so that, when the pinion turns, it drives the piston against the spring to compress it. The pinion shaft projects out of the housing and carries a door closer arm which swings when the pinion turns.
Movement of the piston within the cylindrical bore requires transfer of fluid from one side of the piston to the other. This transfer is effected through fluid passages in the walls of the housing. Generally, the passages are equipped with needle valves or other threaded flow control devices which increase or decrease their projection into the passages according to how much they are turned and in which direction. By this means, fluid flow can be adjusted between wide open and fully closed.
For greater detail of the structure and operation of typical door closers see U.S. Pat. No. 4,386,446 to Zunkel, et al, the specification of which is incorporated herein by reference. When the door is opened, the closer arm turns the pinion which drives the rack and piston against the spring, thereby compressing it. Upon release of the door, the spring drives the piston to turn the pinion, swing the door closer arm, and thereby close the door. Of course, the motion damping action caused by the fluid transfer around the piston works in both directions.
In door closers incorporating regulating valves of the current art the fluid passages are primarily in the housing walls. This requires a great deal of precision drilling and cross drilling as well as threading and fitting. Because of the precision operations required to make closers of that design, there is a higher than normal probability of error. This leads to high rework and scrap losses as well as susceptibility to loss of adjustment.
The foregoing illustrates limitations known to exist in present door closer speed regulating valves. It would, thus, be advantageous to provide an alternative directed to overcoming one or more of those limitations. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.